The present invention relates to thickness measurements, and particularly to non-invasive thickness measurements using electromagnetic waves, which in some embodiments may have particular applicability to measuring thickness of a vehicle tire.
Measuring the thickness of a material can be accomplished in a variety of ways. For example, a material sample may be cut from the material and then physically or optically measured. Alternatively, the material may be punctured by a suitable device, and the thickness measured thereby. However, for some materials, it may be undesirable to damage the material in order to measure the thickness of the material. Accordingly, some physically non-invasive thickness measurement techniques have been developed. For example, U.S. Pat. No. 7,135,869 describes an approach that utilizes a cavity resonator that is closed off by being placed against a coated metallic surface, with the thickness of the coating being determined based on the resulting resonate frequency of the cavity resonator. However, such an approach requires the presence of a metallic substrate, a homogenous coating layer, physical access to the exposed surface of the coating, and that the cavity resonator be placed physically against the coating, some or all of which may be inappropriate for other situations than for testing coating thickness on an aircraft wing.
Thus, while the prior art approaches to thickness measurements may be suitable for some situations, they may not be ideal for all situations. Accordingly, there remains a need for alternative approaches to measuring a thickness of a material, particularly methods that are physically non-invasive, and to corresponding apparatuses.